Copper-base alloy and castings thereof



17, 19-57 F.- A. BADIA ETAL 3,347,566

COPPER-BASE ALLOY AND CASTINGS THEREOF Filed Dec. 27, 1966 F a. 3 Fig.4

INVENTORS FRANK ARTHUR BADIA GARY NEIL KIRBY ATTORNEY United StatesPatent 3,347,666 COPPER-BASE ALLOY AND CASTINGS THEREOF Frank ArthurBadia, Ringwood, N.J., and Gary Neil Kirby, Ann Arbor, Mich, assignorsto The International Nickel Company, Hue, New York, N.Y., a corporationof Delaware Filed Dec. 27, 1966, Ser. No. 613,695 Claims. (Cl. 75-1575)ABSTRACT OF THE DISCLOSURE Chill-cast articles, e.g., permanent moldcastings and die castings, made of alloys containing copper, zinc andphosphorus, with or without nickel. Copper-base alloys havingcompositions characterized by low liquidus temperatures and especiallysuitable for permanent mold casting or die casting.

This is a continuation-in-part of application Serial No. 387,960, filedAugust 6, 1964 now abandoned.

The present invention primarily relates to the production of castarticles, particularly to the production of shock-resistant, ductilepermanent molded or die-cast articles made by casting at low pouring orinjection temperatures.

Heretofore, the art has endeavored to develop cast articles, includingalloys and processes there-for, that enable commercial production ofcastings having a desirable combination of characteristics renderingthem suitable for for a wide variety of purposes where low cost is amajor objective and high strength and high ductility are not especiallyrequired. Such low cost castings include plumbing fixtures, marinefittings and bathroom hardware. Although outstandingly high strength andductility characteristics have not usually been deemed necessary,nonetheless an ultimate tensile strength level of about 45,000 poundsper square inch (p.s.i.) or, advantageously, 55,000 p.s.i. is desirabletogether with yield strengths on the order of about 25,000 p.s.i. andabove. More important, such castings must be characterized by adequateductility and shock resistance which will enable the casting towithstand being broken by moderate blows or by being dropped onto a hardsurface such as of concrete; A moderate level of hardness is alsonecessary in order that the casting will not be easily marred by nicksand scratches, yet the hardness should not be so high as to involvedifiiculty or high cost in machining and finishing. Of course, freedomfrom brittleness is also required for good machinability.

Corrosion resistance is also an important characteristic for suchcastings since in use they are frequently exposed to tap water and tocleaning agents. Too, special applications often involve exposure tocorrosive agents, such as sewage, sea water and industrial gases.Moreover, resistance to stress-corrosion cracking is of particularbenefit in many instances, e.g., exposure to ammonia and resistance toselective corrosion, e.g., dezincification in the case of brass alloys,is also highly desirable since it is too often a serious problem in manysituations.

A white (silver-like) color is also a very advantageous characteristicsince many castings are used in places where the public expects to seemetallic-white surfaces. If the casting is to have a white platedcoating, e.g., chromium plating, when in use, it is required, or atleast highly desirable, that the casting surface be white or near whitein order that the casting does not show a strongly contrasting color itthe white coating does not completely cover the casting or is worn away.In this connection, the

ice

characteristic color of brass and bronze is unsatisfactory in manyapplications.

In respect of the production of low cost castings, permanent mold or diecastings afford many advantages. In their respective processes, metal isgravity poured or injected under pressure against metal molds and coolsrather rapidly, i.e., is chill cast. However, mold or die costs,including costs of maintenance and replacement thereof, contributesubstantially to the overall cost especially where pouring or injectionof the metal must be at such a high temperature as to cause great wearand other de terioration, e.g., heat checking, of the metal molds.While, for many years various well known brasses and bronzes have beenpermanent molded or die cast it is of major importance to note that therelatively high liquidus temperatures of these alloys have necessitatedcorrespondingly high pouring or injection temperatures (the temperatureof the metal when it is fed into the die) and thus have resulted inincurring undesirably high reconditioning and replacement costs. Sincemold or die life can generally be increased when the metal for thecasting can be fed at a lower temperature, it is highly advantageous forproduction of low cost cast articles to provide castings that arecharacterized by relatively low pouring or injection temperature.Present feeding temperatures for commercially available brass diecastings are disadvantageously high, e.g., 1700 F. or higher, and havesubstantial adverse effects on die life. Overcoming the problem ofproviding commercially satisfactory corrosion-resistant articles thatcan be cast at lower temperatures is not so simple as merely making acasting containing a melting point depressant, e.g., tin, silicon orphosphorus, since it is necessary that the articles possess advantageousmetallurgical characteristics, such as those referred to herein. It isespecially noted that elements such as phosphorus, tin and silicongenerally can embrittle copper-base die-casting alloys, particularly abrass alloy. Accordingly, for success, alloy compositions for diecastings must be specially balanced in order to achieve to a highlysatisfactory degree a low feeding temperature, shock resistance,ductility and other advantageous characteristics. Even though themetallurgical art has exerted skill and inventiveness toward overcomingproblems of providing commercially satisfactory permanent mold and diecastings which are characterized by low pouring and injectiontemperatures and has accomplished substantial improvement in this field,even the best of recent improvements in brass castings of which we areaware requires injection temperatures in the range of about 1550" F. toabout 1625 F. for making die castings and normally higher temperaturesfor pouring permanent mold castings.

Although many attempts were made to overcome the foregoing difficultiesand other disadvantages, none, as far as we are aware, was entirelysuccessful when carried into practice commercially on an industrialscale.

It has now been discovered that new cast articles characterized by shockresistance and ductility can be produced by casting special compositionsat low pouring or injection temperatures.

It is an object of the present invention to provide new Other objectsand advantages will become apparent from the following description takenin conjunction with the accompanying drawing, in which:

FIGURES 1, 2, 3 and 4 are reproductions of photomicrographs, taken at amagnificationof 250 diameters (250x), of the cast alloys which are ofchemical compositions in accordance with the invention and which wereetched with an aqueous solution of 10% ferric chloride;

FIGURE 1 shows a chill-cast microstructure in a die casting made of acopper-phosphorus-zinc-nickel alloy;

FIGURE 2 shows a chill-cast microstructure in a die casting formed of acopper-phosphorus-zinc alloy;

FIGURE 3 shows a chill-cast microstructure in a copper-zinc-phosphorusalloy that was chill cast in a metal die mold by gravity pouring(permanent molded); and

FIGURE 4 shows a slowly cooled microstructure in acopper-phosphorus-zinc alloy that was cast in a sand mold and slowlycooled.

Generally speaking, the present invention contemplates cast articles,including plumbing hardware, marine fittings and architectural trim,which are consistently characterized by good shock resistance andductility, particularly in respect of permanent molded articles, andwhich are made of a special copper-base alloy that is capable of beingfed at a low temperature, e.g., about 1285 F. to about 1615" F., inapparatus of the type used in commercial production. The inventionfurther contemplates achieving advantages of reduced wear and decreaseddeterioration of mold and die life which flow from low pouring orinjection temperatures. Of additional advantage, cast articles of theinvention are characterized. by a high order of corrosion resistance, awhiteness in color when in the buffed and/or polished condition and goodhardness. Permanent mold and die castings in accordance herewith areproduced in a chill-cast condition obtained by rapid solidification andit is to be understood that the characteristics of such castings, asreferred to herein, are existent when the castings are in the chill-castcondition. Further, such castings are generally characterized by achill-cast microstructure comprising a copper-zinc solid solution and arefined distribution of complex phosphides of one or more metals fromthe group copper, zinc and nickel. The invention also contemplates a newdie-casting process whereby improved long die life is achievedcomprising injecting a special copper-base alloy at a temperature ofabout 1285 F. to about 1615 F. and at a pressure of at least about 8000p.s.i. into chill mold dies and rapidly cooling and solidifying thealloy.

The special copper-base alloy of which the castingvof the invention ismade contains at least about 2% and not more than about 6.8% phosphorus,about 20% to about 40% zinc, up to about 8% nickel providedthat thepercentage of nickel does not exceed twice the percentage of phosphorusin the alloy and with at least 1.1% nickel being present when thephosphorus content of the alloy is greater than up to about 1% lead andthe balance essentially copper. Moreover, the amounts of phosporus andzinc are specially balanced to characterize the alloy and/or the'castingwith a balance factor which is of a magnitude referred to hereinafterand which is in accordance with the relationship V=percent P+0.16(percent Zn) tor of the alloy composition is from 5.2 to about 10.5andwhen the casting contains less than 1.1% nickel, the

balance factor is 5.2 to 8.9. Thus, the castings are made of a specialalloy. containing 2% to about 6.8% phosphorus, about 20% to about 40%zinc, up to about 1% lead, up to 8% nickel with the balance beingessentially copper, and having the aforesaid composition correlated withrespect to phosphorus, zinc and nickel to characterize the alloy with abalance factor V, which is in accordance with the relationship V=percentP+0.16 (percent Zn) of from 5.2 to about 10.5 and to provide that theamount of nickel is not greater than twice the phosphorus content and isat least 1.1% when the balance factor is greater than 8.9 and upto about10.5 and also whenever the phosphoruscontent is greater than 5%, e.g.,5.1%. This special alloy is characterized by a liquidus temperature-33.3% zinc and balance essentially copper resists with-- out fracturethe shock of being dropped onto concrete from a height of about six feetand has an elongation of at least 1% in a tensile test, whereas the sametype of casting consisting of 4.85% phosphorus, 33.2% zinc and balanceessentially copper and characterized by a balance factor of 10.2 (whichalloy is not in accordance with the invention since it does not containat least 1.1% nickel) is shattered when subjected to the same shocktest. Further, an example of a nickel-containing permanent mold castingcharacterized by a balance factor of 10.3 in accordance with theinvention and which consists of 5.1% phosphorus, 32.4% zinc, 5.7% nickeland balance essentially copper is not fracturedby the shock of asix-foot drop onto-concrete and has at least 1% elongation in a tensiletest. It is also, of course, required that the amounts ofphosphorus,zinc and nickel, ifany, be in accordance with the ranges set forthhereinbefore. In general, if the zinc and/or the phosphorus contents aretoo high, the casting is brittle and if too low, the liquidustemperature is too high with the consequence that the casting cannot beproduced at low pouring or injection temperatures. It also has beenfound, surprisingly, that by having about 2% or more phosphorus thecasting of the invention is characterized in the surface-polishedcondition by whiteness of color, in contrast to the usual brass color ofcopper-base .alloys with zinc, even when the casting does not containnickel.

Nickel in amounts of 1.1% to about 8%, advantageously about 4% to about7%, generally enhances ductility and shock resistance and is especiallyeffective for obtaining adequate ductility and shock resistance when thephosphorus content is high, e.g., about 5% or higher, and/or when thebalance factor is above about 8.9, e.g.,. 9.0, and up to about 10.5. Ingeneral, as the phosphorus content and the balance factor are increased,the liquidus temperature and, thus, the minimum injection temperaturefor the casting are decreased. If the nickel content of the casting istoo high, i.e., greater than about 8%, the

p.s.i. The minimum injection temperature of the alloy is generally about25 F. above the liquidus temperature (about 25 F. superheat) of thealloy being injected, although the degrees of superheat can be greaterthan 25 F., e.g., 50 F., 100 F. or even 200 F., depending upon thesection thickness and geometry of the article being cast. Hi herinjection pressures, e.g., 15,000 p.s.i. or 0,000 psi, can be employedand at such higher injection pressures the injection temperature may benearer the liquidus temperature, e.g., about F. or about 20 F. above theliquidus temperature. Cold chamber machines or other types of diecasting machines that are satisfactory for die casting copper-basealloys can be employed. Oil-fired or gas-fired furnaces can be used formelting the alloy or high frequency furnaces can be used if such areavailable and economic considerations do not dictate otherwise.

In carrying the invention into practice and where an intendedapplication would necessitate the lowest in liquidus temperature, it isadvantageous to produce castings of a copper-phosphorus-zinc-nickelalloy containing 5% to about 6.8% phosphorus, about 22% to about 34%zinc, 1.1% to 8% nickel with the balance being copper, and which has abalance factor V not greater than about 10.5 as computed by the formulaV=percent -P-|-0.16 (percent Zn). This alloy is consistentlycharacterized by an advantageously low liquidus temperature of about1260 F. or lower, e.g., 1252 R, up to about 1475 F. and is alsocharacterized by good s-hock resistance and ductility in the chill-castcondition and can be cast at feed temperatures of about 1285 F. to about1500 F., or higher if desired. Such low temperatures are of substantialbenefit in obtaining improved and prolonged mold or die life. Especiallygood corrosion resistance is obtained when the zinc content of thespecial alloy for castings in accordance herewith is not greater thanabout 27% or 28%, e.g., when zinc is 20% to 28%, or 22% to 28%.

While the balance of the composition Within the invention ischaracterized herein as being essentially copper, it is to be understoodthat the term balance essentially copper as referred to herein does notexclude small amounts of other elements which can be present asimpurities without substantial detrimental effects or which can servesome useful purpose ancillary to the invention. Thus, in accordance withthe invention castings can contain incidental elements and/oringredients such as up to 0.25% iron, desirably not more than 0.1% iron,and up to about 0.1% each of aluminum, titanium, magnesium andberyllium, provided that the sum of such incidental ingredients is belowabout 1% and it is most preferable that all incidental ingredients bekept below their solubility limits in the alloy. The element tin shouldbe kept below about 1%, advantageously no higher than 0.25%, since ittends to render the alloy hot short in the mold and silicon is keptbelow about 0.5%, advantageously not more than 0.2%, in order to avoidembrittlement. Amounts of oxidizable elements such as titanium andaluminum, if present, are not greater than about 0.1% so that thedross-forming effect of these elements does not detract from the cleanand fluid eastability of the alloy. An important practical advantage isthat the castings can tolerate at least up to about 1% lead, e.g., about0.94%, since it not only permits use of lead-containing scrap inprocessing but also allows for the addition of about 0.5% to 1% lead inorder to achieve advantageously good machinability characteristics,e.g., alloy No. 36 in Table II hereinafter.

It is to be understood that the term copper-base, as applied herein,means that the major constituent of the alloy is copper, i.e., that thealloy contains an amount (by weight percent) of copper that is greaterthan the amount of any one other element in the alloy, but does notnecessarily mean that the alloy contains at least 50% copper. Thus, analloy containing 4.1% phosphorus, 40% zinc, 8% nickel, 1% lead, 0.9%impurities and 46% copper is in accordance with the invention and is anembodiment of the special copper-base alloy for the casting and theprocess of the invention.

Where high corrosion resistance coupled with particularly low feedtemperatures, i.e., not higher than about 1385 F., is desired it isadvantageous that the alloys contain about 22% to about 27% zinc, 1.1%to 8% nickel, advantageously with nickel at least about onehalf thephosphorus content, phosphorus in an amount sufficient to characterizethe alloy by a balance factor of about 9.6 to about 10.5 (and thus withat least about 5.3% but not more than about 6.8% phosphorus) with thebalance essentially copper. When of this beneficial composition With upto about 6.8% phosphorus and with the phosphorus content correlated tothe amount of zinc in the alloy so that the balance factor is about 9.6to about 10.5, the alloy is consistently characterized by an especiallylow liquidus temperature of about 1260 F., or lower, to about 1360 F.,and when in the chill-cast condition is characterized by shockresistance and adequate ductility, high resistance to dezincificationand a white color in the surface-polished condition.

For use where a low melting range alloy which does not require nickel isdesired for making shock-resistant and corrosion-resistant castings, thepresent invention contemplates an advantageous alloy compositioncontaining about 24% to about 27% zinc, phosphorus in an amount of 4% to5% and correlated with the amount of zinc to provide that the balancefactor does not exceed 8.9, up to about 4% nickel, and the balanceessentially copper. This allow is characterized by a consistently lowliquidus temperature of about 1360" F., or lower, e.g., 1352 R, up toabout 1480" F.

Where relatively high ductility and particularly good corrosionresistance are of importance or are required and it is not imperativethat the pouring or injection temperature be particularly low, it isadvantageous that an alloy in accordance with the invention containabout 20% to about 28% zinc, phosphorus in an amount of at least 2% andup to an amount sufiicient to characterize the alloy by a balance factorof about 8, i.e., not greater than about 8 (and thus not more than about4.8% phosphorus), up to 8% nickel provided that the percentage of nickeldoes not exceed twice the percentage of phosphorus with balanceessentially copper. Permanent mold castings of such an advantageousalloy composition having a balance factor up to about 8 arecharacterized in the chill-cast condition by an elongation of at leastabout 5%, or higher, e.g., 8% or 10%, and'have a liquidus temperaturenot greater than about 1590" F. With regard to die castings, aphosphorus range of about 2% to 2.5% or 3% together with a zin range of20% to about 28% is considered the most suitable where lowest injectiontemperatures are not necessary.

For the purpose of giving those skilled in the art a betterunderstanding of the invention and a better appreciation of theadvantages of the invention, the following illustrative examples aregiven.

A number of alloys, alloys Nos. 1 through 23, having chemicalcompositions suitable for castings in accordance with the invention areset forth in Table I hereinafter together with liquidus temperatures andvarious mechanical characteristics thereof. The alloys were permanentmold chill cast wedges formed by gravity pouring into meta-l die molds.A gas-fired furnace was used and the cast wedges (from which the tensilespecimens were subsequently taken) were 7 /2 inches in length, 2%.inches in height with a tapering thickness from inch at the top to inchat the bottom. Cast iron molds were employed and were heated to about400 F. for casting. Tensile bar specimens were machined from the /2 inchthickness of the wedges, the specimens being about 1% inches long inreduced section and about 0.252 inch in diameter. In the alloycompositions referred to in Table I, the balance is essentially copper.

TABLE I Percent Mechanical Properties in Liq. Pennanent Mold ConditionAlloy V Temp., No. Factor F.

P Zn Ni U.T.S. Y.S. EL.

(K s.i.) (K 5.1.) percent 6. 64 24. 1 1. 15 10. 5 1, 252 60. 8 43. 6 1.5 5. l 32. 4 5. 7 10. 3 1, 356 62. 9 52.5 1. 5.15 31.9 3. 38 10. 2 1,334 62. 1 50. 3 1. 0 6. 25.3 5. 88 10. 1 1, 319 53. 7 37. 6 1. 5 5. 825. 4 3. 9. 9 1. 288 55. 2 38:7 1. 5 5. 55 25. 8 1. 1 9. 7 1,300 52. 537. 8 1.0 5. 4 24. 9 5. 72 9. 4 1, 404 50. 4 34.1 3. 0 5 27. 3 2. 85 9.4 1, 456 46. 1 28. 8 4. 5 5. 15 24. 5 2. 95 9. 1 1, 383 48. 3 33. 9 2. 03. 02 38 5. 08 9. 1' 1, 466 52. 7 38. 2 1.5 5. 23 25. 9 5. 45 9. 4 1,47448. 7 32. 1 4. 0 3.5 33.3 8.8 1,394 60.3 46.8 1.0 4.6 25.4 8.7 1,35649.0 35.7 1.0 3. 22 33. 6 5. 4 S. 6 1,498 55. 4 29. 8 4. 5 4.5 25.2 8.51,388 53.4 35.9 3.0 2.07 39. 4 8. 4 1, 504 49. 5 36. 7 1. O 4.03 25.98.2 1,412 49.9 30.2 4. 5 3. 31. 1 8. 2 1,460 55. 4 28. 3 4. 0 4. 5 20. 57. 8 1, 500 53.1 28. 4 6. 0 3. 77 25. 3 7. 8 1,482 49. 8 26. 0 9. 0 2.56 32. 9 7. 8 i 1, 472 62. 6 39. 2 5. 5 2. 64 25.6 6. 7 1, 522 51. 3 24.3 10. 5 2. 12 21. 3 5. 5 1, 558 54. 5 25. 2 10. 0

V Balance factor.

U.T .S. Ultimate tensile strength.

Y.S .=Y'1eld strength at 0.2% offset.

K s-.i.='Ihousands of pounds per square inch.

E l.=Percent elongation in one (1) inch gage length.

Liquidus temperature determined by using a of the thermal arrest duringslow cooling of the melt.

Results set forth in Table I confirm that alloys Nos. 1 through 23 areall characterized in the chill-cast permanent molded condition byelongations of at least 1% and by liquidus temperatures not higher thanabout 1590 F. and as low as 1260 F., or lower. In addition, each,

alloy is characterized by ultimate tensile strengths and yield strengthson the order of about 45,000 p.s.i. and about 25,000 p.s.i.,respectively, and higher. Alloys 1 through 11 having V factors of atleast about 9 consistently manifested yield strengths well in excess of27,500 p.s.i. and alloys 13, 15 and 17, with at least 4% phosphorus andwith zinc in the range 24% to 27%, also had at least 27,500 p.s.i. yieldstrength. Castings made of each alloy demonstrated good shock resistanceby successfully withstanding impacts of six-foot drops onto concrete.

With regard to die cast articles, about 500 die castings having chemicalcompositions of alloys Nos. 24

through 37 setforth in Table II were successfully produced in acold-chamber die-casting machine, using an injection pressure of about8800 p.s.i., of a type normally used for production of commercial diecastings. All of thermocouple to measure the temperature the castingsstripped cleanly from the metal dies without any indications of stickingto the dies and no hot-tearing,

cracking or other indications of hot shortness or brit 3 tleness wereencountered. It is to be understood that many factors in addition tofluidity are involved in determining the success of a die-casting alloyand for success in commercial production a die casting must not stick 4O(bond, Weld, braze, etc.) to a casting die and must not be subject tohot shortness. Temperatures at which the castings were actually injectedare also setforth in Table II under Temperature of Injection and showthat examples of the invention were successfully injected for diecasting at temperatures not greater than 1575 F. and as low as 1370 F.The temperatures shown are not neces sarily the lowest temperatures atwhich the alloys could be injected successfully. Tests of die castingsof each of the alloys Nos. 24' through 37 which, of course, were in thechill cast condition, confirmed that the die castings were characterizedby good shock resistance. Alsoset forth in Table II are compositions ofalloys A and. B which contain too much silicon to be in accordance withthe invention and which were found to be brittle.

TABLE 11 Percent Temp. of Shock Alloy Cu Injection, Rcsist- VFaetor F.ance Zn P Ni Other 24 4.6 1,430-1,520 Good--. 8.4 24 4.0 .500 8.4 24 4.61,500 8.4 24 4.9 1,450-1,530 s7 24 4.9 1, 8.7 24 4.9 1, 520 8.7 29 4.21,370-1, 575 8.8 29 4.2 1, 51 8.8 29 4.2 1,495 as 36 2.7 1, 490-1, 5008.5 36 2.7 1,490 8.5 37 2.7 1, 500-1, 525 8.6 37 2.7 0 8.6

37 2.7 1,500 8.6 31 3.2 1,385 Poor.. 8 2 29 5.1 1,340-1,480 do 9.7

Bal.= Balance plus impurities. V= Balance factor.

Die castings having the chemical compositions set forth in Table II werealso tested for machinability by turning threads on the castings.Castings of alloys Nos. 24 through 37 were sufficiently ductile andshock resistant to be machined whereas the castings of alloys A and Bwere brittle and broke up when machining of them was attempted. A whitecolor was generally characteristic of buffed and/or polished surfaces ofcastings of alloys Nos. 24 through 37 with some of the highest degreesof whiteness appearing on surfaces of alloys Nos. 24, 27 and 29.Hardness tests showed that die castings of the invention are generallycharacterized by a moderately high hardness, e.g., Rockwell B80 and 90,somewhat higher than the hardness of commercial brass containing about36% zinc.

A quite unusual and surprising aspect of the invention is that thetensile ductility of permanent mold castings have been found to beconsistently higher, and markedly so, than that of die castings ofotherwise the same or similar composition. This feature, which obtainsover a wide liquidus temperature range, is reflected by the datareported in Tables III and IV. In this regard, alloys 38 through 43 and44 through 52 represent tensile data of die castings and permanent moldcastings, respectively. For convenience, tensile ductility of similarcompositions is also compared in Table III. Alloys 53 through 58, TableIV, are tensile specimens of alloys 38 through 43 which were remeltedand made into permanent mold castings.

tinuous and seemingly form one or more rather continuous paths alongwhich embrittlement failure may occur sooner than otherwise might be thecase. In contrast, while permanent mold castings also manifest a refineddistribution of complex phosphide in a copper-zinc solid solution thephosphide phase is more discontinuous or disrupted.

Refined chill-cast microstructures of die castings in accordance withthe invention are illustrated by FIG. 1, which is of alloy No. 27 (4.9%phosphorus, 24% zinc, 3.3% nickel and balance copper) and by FIG. 2,which is of alloy No. 24 (4.6% phosphorus, 24% zinc and balance copper).FIG. 1 shows a highly refined structure comprising a solid solutionmatrix containing fine precipitates of complex hosphides. The solidsolution is basically of copper and zinc (with a small proportion ofnickel) and appears as the light background. The fine precipitates ofcomplex phosphides vary in shade from light to dark. FIG. 2 shows a darkbackground of an extremely refined eutectic structure made up of acopper-zinc solid solution and complex phosphides. The globularlight-colored precipitates are a primary copper-Zinc solid solution.FIG. 3 illustrates another chill-cast microstructure of an alloycontaining 4.6% phosphorus, 24% zinc and balance copper in accordancewith the invention. The microstructure in FIG. 3 shows a refinedeutectic structure of the type described in connection with FIG. 2 pluslight-colored dendritic needles or plates of the copper-Zinc solidsolution. The small globular dark areas are complex phos- TABLE IIIPercent Elongation, percent Liq. U.T.S., .Y.S., Alloy Temp., K s.i. Ks.i.

Zn Ni P F. Die Perm. Cast Mold n.a.=Not added. 4 Balance of alloyscopper plus impurities.

TABLE IV Percent L U.T.S., K s.i. Elongation 11;.

Alloy Temp,

Zn Ni P F. Die Perm. Die Perm.

Cast Mold Cast Mold Balance of alloys copper plus impurities.

While the theory or mechanism which Would explain the diiferenceexhibited in respect of the tensile ductility of permanent mold and diecastings within the invention is not completely understood, it wouldappear the phosphides which form in the die castings are ratherconphides. FIG. 4 is of an alloy containing 4.6% phosphorus, 24% zincand balance copper and illustrates a slowly cooled microstructure whichis not the microstructure of a chill casting in accordance with theinvention and which, in contradistinction to the chill-castmicrostructures illustrated in FIGS. 1, 2 and 3, is characterized by acoarse and irregular eutectic made up of a copper-zinc solid solutlonand complex phosphides plus dendrites of the copper-zinc solid solution(the coarse light phase). By comparing FIG. 1 with FIG. 2 it is seenthat nickel has a very substantial effect in refining the chill-castmicrostructure of the alloy and the beneficial effect of nickel on theshock resistance and tensile ductility of castings in accordance withthe invention can be attributed to the remarkable refinement of thechill-cast microstructure brought about by nickel additions. The refinedeutectic shown in FIGS. 2 and 3, as compared with the coarse andirregular eutectic shown in FIG. 4, was produced by greater chilling ofthe casting and is advantageous for the purpose of obtaining good shockresistance and ductility in castings which do not contain enough nickelto produce a precipitated structure of the type illustratedin FIG. 1.

To further illustrate the advantageous characteristics and/or propertiesattributable to the novel,;unobvious features of the present invention,a number of alloys, and permanent mold castings thereof, havingcompositions not in accordance with the invention were prepared andtested to compare the mechanical characteristics in the chill-castcondition and the liquidus temperatures thereof with correspondingcharacteristics of alloys in accordance with the invention. Thecompositions of the alloys not in accordance with the invention andcharacteristics pertaining thereto are set forth in Table V hereinafter.The

melting, casting and testing techniques for obtaining the test resultsgiven in Table V were the same asthose for obtaining the results setforth in Table I.

to dezincification and stress-corrosion cracking. In' dezincificationtests, an alloy containing about 6.2% phosphorus, about 26% zinc,about'3.1% nickel with balance copper in accordance with the inventionand in the chill-.

cast condition exhibited superior corrosion resistance as compared tothe corrosion under the same test conditions of a commercial brass alloycontaining about 36% zinc, 1% silicon and balance copper. Thedezincification testing procedure was an acceleratedexposure testwhereby machined bars about three inches long and one-half inch indiameter were immersed for twenty days in a 1% cupric chloride aqueoussolution at 120 F. After twenty days immersion, the alloy of theinvention exhibited excellent resistance to corrosion by dezincificationand showed no evidence of coppering, i.e., redeposition of a porouscopper layer (a result of corrosion by dezincification), whereas thecommercial brass alloy was badly corroded and had undergone extensiveand severe coppering. Re-

TABLE V Percent Mechanical Properties in Liq. Chill-Cast Condition AlloyV Temp.,

Factor F. Zn P Ni U.'1.S. Y.S. El.,

(K s.i.) (K s.i.) Percent 26. 2, 0.95 5.1 1, 724 42. 5 13. 7 42.1 4. 311 1, 452 53.8 38. 7 Nil 31.0 5. 3 10. 3 1, 388 63. 3 50. 8 0.7 24; 2 7.99 11.9 1, 298 33. 5 6.23 11.6 1,308 29 6. 11.1 1, 272 27. 2 6. 13 10. 51, 280 Brittle-Shattered 43.1 2. 6 9. 5 1, 484 Upon Impact 25. 7 5.1 9.2 1, 284 37. 6 3.1 9. l 1, 440 11.8 7.12 9.0 1, 458

Balance of alloys copper plus impurities.

Each of the alloys referred to in Table V is outside the scope of .theinvention, eachof these alloys being unsatisfactory in atleast onerespect for attaining all the objects of the invention. For instance,the amount of phosphorus in alloy C and the balance factor thereof aretoo low to be within the special alloy composition for the invention andits liquidus temperature of 1724 F., is too high to permit die castingat an injection temperature not greater than 1615 F. in accordance withthe invention and thereby achieve prolonged die life. Alloy D is not inaccordance with the invention in respect to Zinc content, nickel contentand balance factor and the alloy is not characterized by adequateductility in the chill-cast condition. The nickel content of alloy E istoo high to be in accordance with the invention and alloy E is notcharacterized by adequate ductility in the permanent moldchill-castcondition. Alloy F is too high in phosphorus, and alloys F, Gand H are too high in respect of the balance factor. Alloy I, with 6.13%phosphorus and a balance factor of 10.5, has a nickel content of 0.65%which is .too low. To be in accordance with the invention an alloy mustcontain at least 1.1% nickel when the phosphorus content of the alloy isgreater than 5% or when the balance factor is greater than 8.9. The zinccontent of alloy J is too highthese alloys, which have balance factorsof 9.2, 9.1 and 9.0, respectively, do not contain an amount of nickelwhich is in accordance with the invention when the balance factor isgreater than 8.9. Each of alloys D through M was brittle in thechill-cast condition and is not satisfactory for making ductile,shock-resistant castings in accordance with the invention. Tensiletestswere not performed on alloys D through M since these alloysexhibited very poor shock resistance when tested by the same impact testwhich was applied to, and was successfully passedby, alloys Nos. 1through 37.

Chill castings of the invention are characterized by unusually highcorrosion resistance including resistance sults of stress-corrosioncracking tests, wherein specimens with alloy compositions of thespecimens, in Table VI hereinafter:

TABLE VI Composition, Alloy Cu Percent Results 1? Z11 Ni S1 59 Bal... 425 No cracking after330 hours in test.

N Bel 36 1 Failed (fractured) due to cracking after 96 hours in test.

Alloys Nos. 59 and 60 are alloys in accordance with the invention andwere tested in the chill-cast condition.

Alloy N is a commercial brass alloy that does not contain an amount ofphosphorus (at least 2% phosphorus) in;

accordance with the invention. The results set forth in Table .VI showthat alloys Nos. 59 and 60 are characterized in the chill-cast conditionby a high order of resistance to stress-corrosion cracking that isclearly different from, and greatly improved over, the stress-corrosioncracking resistance of commercial brass such as alloy N.

The invention provides an improvement in the die casting of copper-basealloys by providing a new die-casting process wherein a specialcopper-base alloy is injected and die-cast articles including plumbingfixtures, architectural castings, bathroom hardware, e.g., faucets,handles and drains, and to cast articles for automobiles, refrigerators,accounting machines, lighting fixtures and instruments includingsurgicai instruments and scientific instruments. In view of theadvantageous characteristics of the advantageous alloy compositions ofthe invention, it will be readily understood by those skilled in the artthat alloy compositions of the invention are widely useful as relativelyinexpensive alloys for making a wide variety of articles for use wherecorrosion resistance, ductility and shock resistance are required.Further, it is also contemplated that copper-base alloys containingphosphorus and zinc, with or without nickel, such as referred to hereinwill be useful for extruded or forged articles for use where corrosionresistance is needed.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to beWithin the purview and scope of the invention and appended claims.

We claim:

1. A shock resistant cast metal article having a chill castmicrostructure comprising a copper-zinc solid solution and a refineddistribution of complex phosphides of at least one metal from the groupconsisting of copper, zinc and nickel and formed of an alloy consistingessentially of 2% to about 6.8% phosphorus, about 20% to about 40% zinc,up to about 1% lead, up to 8% nickel with balance essentially copper andhaving the aforesaid composition correlated with respect to phosphorus,zinc and nickel to characterize the alloy with a balance factor V which,in accordance with the relationship V=percent P+0.16 (percent Zn) isfrom about 5.2 to about 10.5 and to provide that the amount of nickel isnot greater than twice the phosphorus content but is at least 1.1% whenthe balance factor V exceeds 8.9 and is at least 1.1% when thephosphorus content exceeds 5%.

2. A shock resistant permanent mold casting in accordance with claim 1and characterized by a tensile ductility of at least about 1%.

3. A shock resistant die casting in accordance with claim 1 andcharacterized by an ultimate tensile strength on the order of about45,000 psi. or higher.

4. A shock resistant article in accordance with claim 1 wherein thephosphorus content is 2% to about 3%.

5. A shock resistant metal article in accordance with claim 1 in whichthe zinc content is from 20% to about 28%.

6. A shock resistant permanent mold casting in accordance with claim 5wherein the phosphorus is correlated with the zinc such that the balancefactor does not exceed about 8, said permanent mold casting beingcharacterized by a tensile elongation of at least about 5%.

7. A shock resistant die casting in accordance with claim 5 in which thephosphorus does not exceed about 5%.

8. A shock resistant permanent mold casting in accordance with claim 5wherein the phosphorus content is 2% to about 3%.

9. A shock resistant die casting in accordance with claim 5 wherein thephosphorus content is 2% to 3%.

10. An alloy consisting essentially of 4% to 5% phosphorus, about 24% toabout 27% zinc, up to about 4% nickel, up to about 1% lead with balanceessentially copper and having the amounts of phosphorus and zinc in thealloy correlated to characterize the alloy with a balance factor V,which is in accordance with the relationship V=percent P+0.16 (percentZn) not greater than about 8.9 and with a room temperature yieldstrength of at least about 27,500 pounds per square inch when in thechill cast condition.

No references cited.

CHARLES N. LOVELL, Primary Examiner.

1. A SHOCK RESISTANT CAST METAL ARTICLE HAVING A CHILL CASTMICROSTRUCTURE COMPRISING A COPPER-ZINC SOLID SOLUTION AND A REFINEDDISTRIBUTION OF COMPLEX PHOSPHIDES OF AT LEAST ONE METAL FROM THE GROUPCONSISTING OF COPPER, ZINC AND NICKEL AND FORMED OF AN ALLOY CONSISTINGESSENTIALLY OF 2% TO AOBUT 6.8% PHOSPHORUS, ABOUT 20% TO ABOUT 40% ZINC,UP TO ABOUT 1% LEAD, UP TO 8% NICKEL WITH BALANCE ESSENTIALLY COPPER ANDHAVING THE AFORESAID COMPOSITION CORRELATED WITH RESPECT TO PHOSPHORUS,ZINC AND NICKEL TO CHARACTERIZE THE ALLOY WITH A BALANCE FACTOR V WHICH,IN ACCORDANCE WITH THE RELATIONSHIP
 10. AN ALLOY CONSISTING ESSENTIALLYOF 4% TO 5% PHOSPHORUS, ABOUT 24% TO ABOUT 27% ZINC, UP TO ABOUT 4%NICKEL, UP TO ABOUT 1% LEAD WITH BALANCE ESSENTIALLY COPPER AND HAVINGTHE AMOUNTS OF PHOSPHORUS AND ZINC IN THE ALLOY CORRELATED TOCHARACTERIZE THE ALLOY WITH A BALANCE FACTOR V, WHICH IS IN ACCORDANCEWITH THE RELATIONSHIP